With the increasing popularity of white water boating, the provision of water craft which is suitable, safe, and structurally sufficient for this type of recreation is a problem to which considerable attention need be given. In particular, kayak and canoes have been provided which are constructed from a flexible plastic skin to yield upon impact with the water and various obstacles encountered in white water conditions. When using a hull formed from flexible plastic material, such as high-density polyethylene plastic, a supporting framework is necessary to maintain the configuration and structural integrity of the boat under forces of impact with the water and obstacles such as rocks encountered.
Heretofore, frame elements have been provided which have been constructed from solid foam block material in which the foam is semi-resilient to absorb part of the impact.
Tubular framework has also been used which includes hollow frame elements having a rectangular or box cross section such as shown in prior art FIG. 8. The tubular framework members are constructed from flexible plastic, however, due to the cross-sectional configuration of the tubular members, stress is concentrated at the bottom corners of the tubular member resulting in abrading and wearing through of the skin material of the hull along a bottom portion thereof, particularly in the seat areas where weight is concentrated.